Despite an impressive evolution of multi- and hyperspectral sensors, usually called spectrometers, there are still very few or crude ways of obtaining an instantaneous so-called multi- or hyperspectral 2D-image of the environment; i.e. 2D-images with more than three spectral bands. We define a hyperspectral image as an image containing more than ten spectral bands, while a multispectral image has between four and ten bands.
Today's multi- and hyperspectral sensor systems are dependent on spatial and/or spectral scanning to produce the resulting image. Some of these systems are described in the publications:                “Photodiode array Fourier transform spectrometer with improved dynamic range” by T. H. Barnes in Appl. Opt. 24, 3702-3706 (1985),        “Fourier Transform Spectrometer with a Self-scanning Photodiode Array” by T. Okamoto, S. Kawata and S. Minani in Appl. Opt. 23, 269 (1984),        “THRIFTI: tomographic hyperspectral remote imaging Fourier transform interferometer” by Slough, W., J., Rafert, J. B., Rohde, C. A., Hart, C. L., in the Proceedings SPIE Vol. 3393, 207-216, (1998),        “A Visible, Spatially-Modulated Imaging Fourier Transform Spectrometer (SMIFTS) for Astronomical Applications” by Rafert, J. B., Holbert, E. T., Rusk, E. T., Durham, S. E., Caudill, E., Keating, D., Newby, H. in the Bulletin of the American Astronomical Society, 24, 1282, (1992), and        “Polarization interferometer for visible Fourier transform spectrometer of static type” by Tugbayev, V. A. in Proceedings SPIE Vol. 2089, 292, (1994).        
In the case of spatial scanning the sensor system captures whole spectra instantaneously, but only for a small region of the scene at each instant of time, and spatial scanning is used to cover the whole scene. This can be achieved by, for example, using a line of sensor elements translated across the scene to be imaged, which is the way most multi- and hyperspectral images are generated, cf. aerial and satellite images as well as in industrial inspection. The converse holds for spectral scanning, thus requiring time to obtain complete spectra. Spectral scanning can be achieved by, for instance, using a filter wheel containing a number of different narrow or broad band filters, and exactly the same scene must be registered using each of these filters.
A disadvantage associated with the need of scanning procedures, is that the resulting image is sensitive to changes in the scene faster than the scanning time. This is in particular severe for close range imaging for fast varying events. The present invention aims at capturing instantaneous multi- and hyperspectral 2D-images when no filter interchange or exchange is performed, i.e. no spectral scanning of the scene is required.
Digital colour cameras can produce instantaneous RGB (Red, Green, Blue) colour images, using colour filter mosaics (e.g. the Bayer colour filter array) integrated with the image sensor chip. The used colour filter mosaics may consist of RGB, RGBE (E=Emerald), CMY (Cyan, Magenta, Yellow) or CMYG colour regions. Processing the responses of the sensors behind the different coloured regions of the used mosaic produces the final RGB image.
In other words, three or four broad-spectral-band filters are used to produce an RGB image; a 3-colour-bands image. An extension to this technique can be the use of a number of high quality narrow band filter mosaics to produce an image with as many bands as the number of the different filters used in the mosaic, cf. U.S. Pat. No. 4,885,634 showing an endoscope for display of monochrome and colour images, where an optical endoscope is connected to a TV camera and an image signal processor for specific spectral-wavelength components, and display means for a monochrome image with respect to a specific wavelength region along with a normal colour image. However, the high cost of this approach limits its usefulness.
Publication “Static polarization interference imaging spectrometer (SPIIS)” by Zhang, C., Bin, X., Zhao, B., in Proceedings SPIE Vol. 4087, p. 957, (2000), teaches a new technology in development that can be used for instantaneous hyperspectral imaging.